Is there anyone of out thar that have experienve with Sudoku2 from fingerarts on the iPad/iPhone.

I have used it for a while. While the user interface is quite nice, I find the expert-level some times too difficult. Some of them are easilly solved using a two-string kite, a fish, sky-scraper or an xy-wing. But others seems completely unsolvable. As a test, I have ran several of them through SudoCue, to help find a solution, but it it surrenders!

Are there anyone of you having experience solving them without guessing?